A Nasa photo of the B-52B mothership carrying the X-43A scramjet on the nose of a modified Pegasus booster rocket en route to breaking its own record. (AFP)

Los Angeles, Nov. 17 (Reuters): An unmanned experimental jet broke a world record for speed on Tuesday, cruising over the Pacific Ocean at just under 7,000 miles per hour in a Nasa test of cutting-edge 'scramjet' engine technology.

The X-43A aircraft flew at a speed of around Mach 9.6 ' nearly 10 times the speed of sound ' after a booster rocket took it to around 110,000 feet and then separated.

A modified B-52 airplane had carried the experimental plane and booster aloft.

It was the last of three test launches for the X-43A series and its supersonic-combustion ramjet or 'scramjet' engine. The scramjet scoops up oxygen from the air rather than carrying liquid oxygen in a tank like an ordinary rocket.

Scramjet technology, Nasa has said, could open the way to cheaper, safer and faster flights into the upper atmosphere, with smaller and lighter craft.

'I think it's easier than people think it is. We can really do this stuff. I don't mean to make it sound too easy, but it's definitely doable,' said Randy Voland, a senior research engineer on the project, at a news conference after the test.

The eight-year, $230-million programme got off to a rough start in June 2001 when the first X-43A and its booster rocket had to be destroyed in mid-air. The second attempt, in March of this year, successfully reached a speed of Mach 7.